Get First Cat as Adult, Double Allergy Risk

Dec. 29, 2011 -- Adults who get their first cat double their risk of cat allergy -- especially if the cat is allowed in the bedroom.

But adults who had cats as kids are less likely to become allergic to their new feline pets, a large European study finds.

An adult's risk of developing a new cat allergy over a nine-year period "was nearly doubled in those acquiring a cat," report Mario Olivieri, MD, of the University of Verona, Italy, and colleagues. "Interestingly, this effect was confined to those allowing a cat in the bedroom."

Olivieri and colleagues collected data on cat ownership during a multicenter study of asthma. They collected cat ownership data and blood tests for various allergies in people aged 20 to 44 years who were not allergic to cats. The 6,292 study participants were tested again nine years later.

Over that time, more than 10% of the study participants got a pet cat. Nearly 4% of them became allergic to cats. Risk of cat allergy was three to four times higher among those who already were allergic to things besides cats.

Getting a new cat raised cat allergy risk by 85%. However, none of those who kept the cat out of the bedroom developed cat allergy.

People who had a cat during childhood had a lower risk of developing cat allergy when they got a new cat as adults. Other researchers have reported the same finding.

"The effect of exposure to high doses of cat allergens seemed to be different at different ages," Olivieri and colleagues note.

Although getting a cat for the kids may well protect them against becoming allergic to cats, the researchers warn that parents should consider their own risk of cat allergy.

The findings appear in the December issue of the Journal of Allergy and Clinical Immunology.